Midfielder Miguel Pallardo has signed a new one-year deal with newly-promoted Hearts while Danny Wilson leaves.
Liam Rosenior has thanked the fans of Hull City for "five wonderful years".
The likes of Chelsea and Arsenal are thought to be weighing up moves to lure Oxford away from Upton Park.
Oxford is highly-regarded within the corridors of power at Upton Park and is tipped for a big future in the game.
The England Under 16 international has been earning reviews in the West Ham academy and this has alerted other clubs to his potential and talent.
West Ham are determined to keep hold of Oxford and are ready to offer the centre-back a deal which would make him one of the best paid youngsters at the club.